The present invention relates generally to a clutch lever with a lever ratio that varies during movement of the clutch lever to maximize both clamp load and clutch lift.
A clutch is utilized to selectively transmit rotation between a drive engine and a transmission. When the clutch is engaged, the clutch lever presses a pressure plate to engage adjacent clutch discs, transmitting rotation between the engine and the transmission. When the clutch is disengaged, the clutch lever is lifted from the pressure plate, releasing the pressure plate from the clutch discs and allowing the clutch discs to rotate relative to the flywheel and the clutch cover, disengaging the engine from the transmission.
The clutch lever provides a force to the pressure plate which is proportional to the lever ratio. A proper lever ratio selection of the clutch lever is important for good clutch performance. In prior clutch assemblies, the clutch lever is usually designated to produce a constant lever ratio.
It is important that the lever ratio be large enough to transmit torque and create an acceptable clamp load level. However, if the lever ratio is large, the pressure plate lift decreases as there is less clearance, or clutch lift, between the pressure plate and the flywheel. For this reason, if the lever ratio is too large, the probability of clutch drag increases. Generally, optimizing clamp load is prioritized over clutch lift, but these competing factors do limit the design of clutches.
Hence, there is a need in the art for a clutch lever with a variable lever ratio to maximize both clamp load and clutch lift.
The present invention relates to a clutch lever with a lever ratio that varies during movement of the clutch lever to maximize both clamp load and clutch lift.
A plurality of clutch levers in a clutch transmit rotation between an engine and a transmission. Each clutch lever includes an inner portion received in an axially moving retainer, an intermediate portion contacting the pressure plate, and a pivoting outer point. A center of curvature of the intermediate fulcrum contact is positioned on the same level as the point of contact of the intermediate portion and the pressure plate, and a center of curvature of the inner fulcrum contact is positioned on the same level as the point of contact of the inner portion and the retainer.
The lever shape is defined by the angle formed by lines extending from the outer point to the intermediate center of curvature and from the outer point to the inner center of curvature. The clutch levers provide force to the pressure plate which is proportional to a lever ratio. The lever ratio is defined by the radial distance from the inner center of curvature to the outer point divided by the radial distance from the intermediate center of curvature to the outer point.
As the clutch levers have the outer point, the intermediate center of curvature and the inner center of curvatures non co-linear, the lever ratio changes as the lever position changes. The clutch levers are designed such that as the clutch levers move from an engaged position to a disengaged position, the lever ratio decreases. As the lever ratio is variable, it is possible to improve both clamp load and clutch lift by selecting the lever shape and changing the lever position. When the clutch is engaged, the lever ratio is large, allowing for large clamp load. When the clutch is disengaged, the lever ratio is small, allowing for large clutch lift.
Accordingly, the present invention provides a clutch lever with a lever ratio that varies during movement of the clutch lever to maximize both clamp load and clutch lift.
These and other features of the present invention will be best understood from the following specification and drawings.